This invention relates to a method and device for detecting a blocked condition in a tube of a liquid infusion pump.
A device for this purpose structured as shown in FIG. 2 has been known. In FIG. 2, numeral 6 indicates a flexible tube for. transporting a liquid therethrough and a mobile coil 7 is disposed in contact with the outer wall of this flexible tube 6 When the internal pressure of this tube 6 changes, the external diameter of the tube 6 also changes correspondingly and the coil 7 is displaced accordingly. A fixed axis 8 is inserted inside the coil 7 such that there is a coaxial relationship therebetween. A biasing spring 9 is provided with one end attached to the fixed axis 8 such that the coil 7 is constantly pressed against the tube 6. A magnet core 10 is disposed inside the fixed axis 8 such that there will be a change in inductance if the coil 7 moves along the axis 8 and this is how a change in the external diameter of the tube 6 is detected. With a detector thus structured, however, the lead wires of the coil 7 are likely to break because the coil 7 keeps moving all the time.